Embodiments of the present invention are generally related to determining ablation treatments for laser eye treatment surgery. The invention provides systems and methods for determining ablation treatments based on a tilted orientation of a patient's eye.
Known laser eye surgery procedures generally employ an ultraviolet or infrared laser to remove a microscopic layer of stromal tissue from the cornea of the eye. Examples of laser eye surgery procedures include photorefractive keratectomy (PRK), phototherapeutic keratectomy (PTK), laser assisted in situ keratomileusis (LASIK), laser epithelial keratomileusis (LASEK), and the like. A laser typically removes a selected shape of a corneal tissue, often to correct refractive errors of an eye. Ultraviolet laser ablation results in photodecomposition of a corneal tissue, but generally does not cause significant thermal damage to adjacent and underlying tissues of an eye. Irradiated molecules are broken into smaller volatile fragments photochemically, directly breaking intermolecular bonds.
Laser ablation procedures can remove a targeted amount stroma of a cornea to change a cornea's contour for varying purposes, such as for correcting myopia, hyperopia, astigmatism, and the like. Control over a distribution of ablation energy across a cornea may be provided by a variety of systems and methods, including use of ablatable masks, fixed and moveable apertures, controlled scanning systems, eye movement tracking mechanisms, and the like. In known systems, a laser beam often comprises a series of discrete pulses of laser light energy, with a total shape and amount of tissue removed being determined by a shape, size, location, and/or number of laser energy pulses impinging on a cornea. A variety of algorithms may be used to calculate the pattern of laser pulses used to reshape a cornea so as to correct a refractive error of an eye. Known systems make use of a variety of forms of lasers and laser energy to effect a correction, including infrared lasers, ultraviolet lasers, femtosecond lasers, wavelength multiplied solid-state lasers, and the like. Alternative vision correction techniques make use of radial incisions in a cornea, intraocular lenses, removable corneal support structures, and the like.
Known corneal correction treatment methods have generally been successful in correcting standard vision errors, such as myopia, hyperopia, astigmatism, and the like. By customizing an ablation pattern based on wavefront measurements, it may be possible to correct minor aberrations so as to reliably and repeatedly provide visual acuity greater than 20/20. Such detailed corrections will benefit from an extremely accurate ablation of tissue.
Known methods for calculation of a customized ablation pattern using wavefront sensor data generally involves mathematically modeling a surface of the cornea using expansion series techniques. More specifically, Zernike polynomials have been employed to model the corneal surface and refractive aberrations of the eye. Coefficients of a Zernike polynomial are derived through known fitting techniques, and an optical correction procedure is then determined using a shape indicated by a mathematical series expansion model.
Known methodology for determining laser ablation treatments based on wavefront sensor data and spectacles often provides real benefits to patients in need thereof. Yet further advancement in ablation technique technology, particularly for refractive correction purposes, is desired. Embodiments of the present invention provide solutions for at least some of these outstanding needs.